Voltage regulator for generators



J. W. ALLEN Filed April 23, 1945 VOLTAGE REGULATOR FOR GENERATORS Aug. 12, 1947.

J. W. ALLEN.

9% QWL GAP (mrrm win) Patented Aug. 12, 1947 UNITED STATES PATENT OFFICE VOLTAGE REGULATOR FOR GENERATORS Joseph Allen, Washington, D. C. Application April 23, 1945, Serial No. 589,832

6 Claims.

(Granted'under' the act of March amended April 30, 1928; 370 O. G. 757) This invention relates to voltage regulators of the carbon pile type, and more particularly to means for maintaining a uniform pressure on the discs of the carbon pile as the discs are reduced in thickness by wear.

Among the several objects of are:

To provide means to compensate for the varying resultant pressure on the carbon pile discs as the gap increases between the voltage coil and the armature attached to the spring which presses the discs together;

To device a voltage regulator capable of holding the output voltage or a generator at a more nearly uniiorm value through greater wear of the carbon pile discs than do prior art devices known to me.

In the drawings:

Fig. 1 shows the relation between the voltage of the generator and the gap, in arbitrary units, between the armature attached to the pressure spring and the voltage coil;

Fig. 2 is an axial section of the essential parts of ordinary type oi! carbon pile regulator;

Fig. 3 is an axial view of the parts of a carbon pile regulator with which my invention is most immediately concerned but with the spring and carbon pile omitted for clearness;

Fig. 4 shows the relation between the pull on the armature and the gap between the armature and the coil and the modification thereof eflected by my invention;

Fig. 5 is a graph showing the voltage-gap characteristic of a voltage regulator modified according to my invention; 4

Fig. 6 is an axial section of a further embodiment of my present invention.

Controlling the output voltage of a generator having a shunt field winding, by means of a carbon pile regulator, is well known. In such devices a pile of thin carbon discs is connected in series with the shunt field winding, with a spring to hold the discs in firm contact together. A voltage coil opposes the action of the spring, and the parts are so adjusted that the fiow oi current through the carbon pile and through the field this invention is such as to give the desired output voltage.

When the voltage rises, for any reason, the voltage coil exerts a greater pull in opposition to the spring, the pressure on the discs is diminished and the increased resistance of the pile cuts down the field current until the voltage is reduced to the normal working value.

However, the effective pull of the voltage'coil on the armature decreases rapidly as the gap bea, 1883, as

tween the armature and coil increases. The result is that after the discs have worn to a certain extent the armature is at such a distance from the coil that the latter does not sufliciently offset the pressure of the spring, the discs are pressed together too tightly and the voltage rises, sometimes to a value that damages the equipment. After further wear of the discs the strain in the spring is released to such an extent that the pressure on the discs is reduced so the resistance oi the pile increases and the voltage drops. It is thus apparent that the difference between the pull of the coil and the force exerted by the spring first increases to a maximum value and then decreases as the displacement of the armature from its original position with respect to the coil becomes greater.

The present invention provides means to secure more nearly uniform voltage regulation over the whole range of movement or the armature due to the wear of the discs. This is effected by auxiliary means that give increasing pull on the armature up to the point that the preponderance of spring pressure over pull of the voltage coil begins to decrease and then itself decreases.

Fig. 2 depicts the essential parts oi'a type of voltage regulator in wide use. Centrally disposed in the housing 8 is a core 9 in threaded engagement with the housing to provide for adjustment of the position of the core. Coil I0 is disposed in housing 8 around core 9 and is connected across the generator, providing an electromagnetic device that is responsive to voltage changes in the output of the generator. The pile H of carbon discs is held .under pressure between 9. member I! carried by spring i3 and a. screw it threaded into closure 15 secured to housing 8. Spring I3 is supported at its ends on sloping abutments l6 and carries an armature IT. The strain in spring I3 is adjusted by means of screw ll to obtain the pressure on pile H that will provide in pile II the proper resistance to maintain the desired output voltage. It is, of course, understood that the actual pressure exerted on pile l I is the preponderance of the thrust I of spring i3 over the opposing pull on armature l1 due to the flux set up by coil l0, which is connected as a voltage coil across the generator.

Fig. 1 shows diagrammatically the characteristics of a regulator like that above described, with the desired voltage value indicated by the dotted line through B, C and E. Curve l8 shows the output voltage in relation to the gap between armature IT and coreil. When screw I4 is adjusted to make the gap very small, the spring l3 is considerably strained and, since it follows Hookes law, reacts strongly on pile l I so that the flux of coil ll does not sufllciently reduce the pressure on the pile and the voltage is high, but decreases rapidly and non-linearly from A to B as the backing oil of screw ll permits widening of the gap. It is to be understood that the units of gap width have an arbitrary assigned value. The usual adjustment is such th'at the voltage is held substantially uniform during such wear of the discs of pile II as changes the gap through the distance between the points B and C, Fig. 1. It will be observed that from point C the voltage increases rather rapidly to the point D. This is because the width of the gap reduces the effect of coil ID in opposing spring II and the pressure applied to pile l I so reduces the resistance of the pile that the field current is augmented and the voltage builds up.

The gap increasing from three units. due to further wear of the discs, the strain in spring I3 is increasingly released and insuflicient pressure is applied to the pile II to keep the voltage up. It is apparent from curve 18 that the device of Fig. 2 does not operate satisfactorily when wear of the discs has proceeded past the stage that gives a gap width much beyond the value represented at the point C.

Fig. 3 illustrates one embodiment of the present invention for favorably modifying the undesirable characteristics of the regulator above described. For simplicity of drawing there are shown on the armature and the electromagnetic portion of the unit, but it is to be understood that in practice the armature i1 is attached to a spring such as I! in Fig. 2. Core 9' has an axial bore tapped at one end to receive and to have threaded engagement with auxiliary core I! that is adjusted to project beyond the face of core 2' into an opening 20 in armature II.

The variation of pull exerted upon armature H by auxiliary core l9 depends upon the extent to which the auxiliary core is inserted into the hole in the armature as is well known to those skilled in the art, and is shown graphically by dotted curve 2| in Fig. 4, the gap units being arbitrary. The gap-pull characteristics of the fiux set up by coil ll acting upon armature I1 is illustrated by full line curve 22 in Fig. 4 and the resultant of adding curves 2i and 22 is depicted in dotand-dash line 22 in Fig. 4. The points on curves 2|, 22 and 23 where these curves intersect vertical lines I, 2, 3 and 4 in Fig. 4 give the values of the pull on armature ll' when the face thereof adjacent housing 8 is at the positions respectively indicated by the same numerals in Fig. 3. It will be noted that the resultant pull on armature I1 is uniform, for all practical purposes, from position 1 to position 3. This device will thus give a substantially constant pull throughout a considerable degree of wear of the discs after which the pull will decrease 'at the time the pressure of the spring is appreciably diminished.

The curve ll of Fig. 1 is thus modified to the curve 24 in Fig. 5, so that the voltage remains substantially constant throughout the wear of the discs covered by Fig. 5 from B to E, and thereafter it decreases, indicating the need of replacing the discs, without the dangerous rise in voltage shown by Fig. 1.

The regulator is assembled with the end of auxiliary core I! fiush with the face at the free end of th core 9 and the latter is adjusted to give the characteristic shown by curve i8, Fig. 1.

4 The auxiliary core is is then screwed into core I to cause the auxiliary core to extend into armature H to give the characteristic shown by curve 24, Fig. 5.

Another embodiment of my invention is depicted in Fig. 6. The core I" is provided with an axial bore 26 through which passes a stem 2| having fixed on one end thereof an armature l1" and on the other end a magnetic plunger 21 which is movable in solenoid coil 2' connected to a source of excitation, which may be the generator.

The regulator is adjusted so that the longitudinal center of plunger 21 coincides with that of coils 2| when the armature I1" is set at a point corresponding to B,F1g. 5. As shown in the small graph in Fig. 6, the pull on plunger 21 by solenoid 20 increases as wear of the carbon discs permits the plunger to be displaced more and move toward the right by the spring (not shown). When half the length of the plunger is out of the coil the pull begins to decrease and practically vanishes when the plunger leaves the coil. The proportioning of plunger 21 and coil 20 to obtain the desired gap-pull characteristic through the working range of the device is well known to those skilled in the art. Thus a voltage-gap characteristic similar to curve 24 can be obtained and the useful operational life of a pile of carbon discs can be greatly extended.

As the discs wear, permitting greater displacement of armature II" from core 0", thereby diminishing the pull exerted upon the armature by coil ll, there is augmented pull applied to the armature by solenoid 2| and plunger 21 to balance the effect of the spring. The position of plunger 21 in solenoid 20 at which the pull begins to decline is such that the eifort of the spring tending to move armature I1" away from core 0" also lessens and thus there is applied to the carbon discs a pressure that is substantially uniform for all practical purposes. The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. In a voltage regulator having a carbon pile, a spring mounted to apply pressure thereto, an armature fixed to the spring, and a voltage coil disposed to attract the armature in opposition to the spring when the coil is energized; an axially bored core in said coil, a stem extending through the core and fixed at one end to the armature, a solenoid plunger fixed to the other end of the stem, and a solenoid disposed around the plunger and connected across a source of energizing current as a voltage coil, whereby said solenoid and plunger oppose the action of the spring when the plunger is moved toward the pile from its equilibrium position in the solenoid and having a pull characteristic that initially increases to a maximum as the plunger is shifted from said position by movement of the armature away from the coil and then decreases upon continued movement of the armature, so that the eifective pressure of the spring upon the carbon pile is substantially the same in all positions of the armature at equal output voltages.

2. In a voltage regulator having a carbon pile, a spring mounted to apply pressure thereto, an armature fixed to the spring, and a voltage coil disposed to attract the armature in opposition to the spring when the coil is energised; an axially bored core in said coil, a stem extending through the core and fixed at one end to the armature, a solenoid plunger fixed to theother end of the stem, and a solenoid disposed around the plunger and connected to a source of energizing current, whereby said solenoid and plunger opposes the action of the spring when the plunger is moved toward the pile from its equilibrium position in the solenoid and having a pull characteristic that initially increases to a maximum as the plunger is shifted from said position by movement of the armature away from the. coil and then decreases upon continued movement 01 the armature, so that the effective pressure of the spring upon the carbon pile is substantially the same in all positions of the armature at equal output voltages.

p 3. In a voltage regulator having a carbon pile, a spring mounted to apply pressure thereto, an armature fixed to the spring, and a voltage coil disposed to attract the armature in opposition to the spring when the coil is energized: a stern connected at one end to the armature and having a solenoid plunger at its other end, and a solenoid disposed around the plunger and connected to a source of energizing current, whereby said solenoid and plunger applying to the armature a pull in opposition to the spring when the plunger is moved toward the pile from its equilibrium position in the solenoid, said pull varying as a function of the extent of such movement to maintain normally a substantially constant difference between the force exerted by the spring on the one hand and the sum of the attraction or said coil and the pull or said plunger and solenoid on the other hand.

4. In a voltage regulator having a pressurecontrolled variable resistance unit, a spring mounted to apply pressure thereto, an armature fixed to the spring, and a voltage coil disposed to attract the armature in opposition to the spring when the coil is energized: a stem connected at one end to the armature and having a solenoid plunger at its other end, and a solenoid disposed around the plunger and connected to a source of energizing current, whereby said solenoid and plunger apply to the armature a pull in opposition to the spring when the plunger is moved toward the pile from its equilibrium position in the solenoid, said pull varying as a function of the extent of such movement to maintain normally a substantially constant diiiference between the force exerted by the spring on the one hand and the sum of the attraction of said coil and the pull of said plunger and solenoid on the other and.

5. In a voltage regulator having a pressurecontrolled variable resistance unit, a spring mounted to apply pressure thereto, and a voltage coil disposed to attract the armature in opposition to the spring when the coil is energized: an armature having a hole therethrough, and an auxiliary magnetic element mounted to extend into the hole in the armature when the armature is an initial position said element to be of such a length that its extremity appear at the mouth of said hole when the armature is intermediate said initial position and the position of maximum displacement of the armature away from the coil, whereby the pull of said auxiliary element being additive to that of the coil and augmenting as the displacement of the armature increases to approximately said intermediate position and thereafter decreasing to said position of maximum displacement to maintain normally over-the whole range of displacement of the armature a substantially uniform diiIerence between the pull of the coil and that of the auxiliary element on the one hand and the force exerted by the spring on the other hand.

6. The apparatus as described in claim 5, wherein the pressure-controlled variable resistance unit is a carbon pile.

JOSEPH W. ALLEN.

REFERENCES CITED The following references are of record in the Certificate of Correction Patent No. 2,425,296.

It is hereby certified that errors read devise; column 3, line 33, for read coil; column 5, line 26,

conform to the record of the case in on the claim 3, for Letters Patent should be read with these corrections 9 the Patent Oifice.

Signed and sealed this 16th day of December, A. D. 1947.

August 12, 1947.

JOSEPH W. ALLEN appear in the umbered atent re uiri correction as follows: n p q ng read only the; column 4, line 14, for "coils applying read app printed specification of the above Column 1, line 13, for device ly; and that the said therein that the same may THOMAS FIMURPHY, Q

Assistant 00mmLm'oner of Patents. 

